There were 136 emergency hyperglycaemic admissions to Baragwanath Hospital over a 6-month period during 1992-1993, representing 1.2% of the total number of medical admissions; 24 (18%) patients died. Diabetic keto-acidosis (DKA) accounted for 88 (65%) admissions (mortality rate 9%) while 16 admissions (12%) were as a result of hyperosmolar non-ketotic coma (HNKC), defined as hyperglycaemia, dehydration and an altered level of consciousness with a plasma osmolality > or = 330 and an arterial pH > or = 7.30, with absent or minimal ketonuria. Of these 16 patients, 9 (56%) were known to have diabetes mellitus. Patients with HNKC were significantly older than those with DKA (P < 0.001) and other patients with nonketotic hyperglycaemia (P < 0.05). The overall mortality rate was 44%; prophylactic low-molecular-weight heparin appeared of benefit (P < 0.05).